1. Field of the Invention
This invention relates to air pollution control. More specifically, the invention is directed to systems and methods for insuring oxidation for oxidizable materials in waste gas streams, and particularly by means of a waste gas purifier such as a catalytic oxidation unit. More particularly, the invention relates to systems and methods for protecting the waste gas purifier from certain predetermined harmful conditions.
2. Description of the Prior Art
Considerable effort has gone into removing harmful materials present in waste gas streams such as would be present in industrial plants such as those waste gases produced in the production of maleic anhydride. In developing waste gas purification units for such waste gas streams, one problem that commonly arises is that the purification unit can be seriously damaged or destroyed by unusual amounts of impurities in waste gas streams, too high of a temperature in the waste gas stream, too high of a pressure in the waste gas stream, or the like.
Systems for diverting the waste gas stream from the purification unit upon detection of one of these harmful conditions to the purification unit has been developed in the past for applications such as the purification of exhaust gases from internal combustion engines, such as is taught in U.S. Pat. No. 3,273,971, incorporated herein by reference. However, these prior art systems such as that of U.S. Pat. No. 3,273,971 are not acceptable when applied to systems wherein the source of the waste gases is a pressure sensitive source such as a scrubber unit from a maleic anhydride plant. Pressures above about 5 psig will cause damage to equipment in the system. On the other hand, rapid loss of pressure results in process failure due to entrainment of liquid in the waste gas stream and resulting problems due to venting of the entrained liquid, damage to the scrubber unit, and/or damage to the waste gas purification unit.